1. Field of the Invention
The present invention relates to a fingerprint verification device and a fingerprint verification method, which are directed to a fingerprint verification scheme performed by verifying fingerprint data being searched with filed fingerprint data.
2. Description of the Related Art
Conventional fingerprint verification has representative verification schemes including an axis verification scheme and an alignment verification scheme.
The axis verification scheme is characterized by a verification process of searched fingerprint feature points and filed fingerprint feature points whose positions are represented in a two-axis coordinate system based on a coordinate reference point (a coordinate position of a singular point such as a core and a delta) which is preset in filed fingerprint data.
The alignment verification scheme is characterized by a verification process of searched fingerprint feature points and filed fingerprint feature points whose positions are represented in a two-axis coordinate system based on a coordinate reference point which is calculated by an adjusting process without using a coordinate reference point preset in filed fingerprint data.
Prior art documents relating to the fingerprint verification includes the following: JP-A-H10(1998)-105711, JP-A-2001-067474, and JP-A-2002-269562.
The axis verification scheme can provide a significantly high verification precision for the verification of taken fingerprints (which most probably have a singular point such as a core and a delta), because the use of the singular point as the coordinate reference point can make it possible to clearly distinguish the feature point arrangements around the coordinate reference point and because high image quality is available. On the other hand, for the left-behind fingerprints verification in which the feature point data are only partially available and the singular point or the like cannot easily be set as the coordinate reference point, a hypothetical coordinate reference point (the center of the fingerprint impression image) is often used. Displacement thus occurs between the coordinate positions of the searched fingerprint feature points relative to the coordinate reference point and the positions on the real image. The image quality is also often inferior. There has therefore been a problem in which an inaccurate or falsely-recognized coordinate arrangement may happen and much lower verification precision may occur.
The alignment verification scheme determines the coordinate reference point from the data arrangement using a coordinate matching amount without using a predetermined coordinate reference point. The verification based on a false coordinate position may thus occur less often, thereby resulting in a high verification precision for the left-behind fingerprints verification. On the other hand, there has been a problem in which the alignment process needs an enormous amount of process, thereby resulting in much lower verification performance than the above-mentioned verification scheme.
Different fingerprint verification system needs to be constructed for each fingerprint verification engine to be used and for each use, so that the system construction is extremely expensive.